This topic focuses on germ cell testicular cancer. You can contact the cancer support specialists at Macmillan for more information about Leydig cell tumour and Sertoli cell tumours. The helpline number is 0808 808 00 00 and is open Monday to Friday, 9am to 8pm.

How common is testicular cancer?

Testicular cancer is a relatively rare type of cancer, accounting for just 1% of all cancers that occur in men. Around 2,200 men are diagnosed with testicular cancer each year in the UK.

Testicular cancer is unusual compared with other cancers because it tends to affect younger men. Although it's relatively uncommon overall, testicular cancer is the most common type of cancer to affect men between the ages of 15 and 49.

For reasons that are unclear, white men have a higher risk of developing testicular cancer than men from other ethnic groups.

The number of cases of testicular cancer diagnosed each year in the UK has roughly doubled since the mid-1970s. Again, the reasons for this are unclear.

Causes of testicular cancer

The exact cause or causes of testicular cancer are unknown, but a number of factors have been identified that increase a man's risk of developing it. The three main risk factors are described below.

Undescended testicles

Around 3 to 5% of boys are born with their testicles inside their abdomen. They usually descend into the scrotum during the first year of life, but in some boys the testicles don't descend.

In most cases, testicles that don't descend by the time a boy is a year old descend at a later stage. If the testicles don't descend naturally, an operation known as an orchidopexy can be carried out to move the testicles into the correct position inside the scrotum.

It's important that undescended testicles move down into the scrotum during early childhood because boys with undescended testicles have a higher risk of developing testicular cancer than boys whose testicles descend normally. It's also much easier to observe the testicles when they're in the scrotum.

Men with undescended testicles are about three times more likely to develop testicular cancer than men whose testicles descend at birth or shortly after.

Family history

Having a close relative with a history of testicular cancer or an undescended testicle increases your risk of also developing it.

For example, if your father had testicular cancer, you're around 4 times more likely to develop it than someone with no family history of the condition. If your brother had testicular cancer, you're about 8 times more likely to develop it.

Current research suggests a number of genes may be involved in the development of testicular cancer in families where more than one person has had the condition. This is an ongoing area of research in which patients and their families may be asked to take part.

Previous testicular cancer

Men who've previously been diagnosed with testicular cancer are between 4 and 12 times more likely to develop it in the other testicle.